Cheap filters are like cheap lenses. You better avoid them if you want good pictures. If you want cheap filters, I bought polaroid filters on amazon for my 18-135 last year for 21$, unfortunately they aren't available anymore from amazon directly. I used them a few times for tests shots, got really bad contrast and sharpness and stopped using them. Then I got a real Hoya Circular Polarizer for my biggest lens, with a few metal step down adapters from ebay so it fits all my lens.
Also, using a cheap UV filter will also make your pictures worse (less sharp). You may protect your lens, but a scratched lens doesn't necessarily take bad pictures. Here's an article about pictures taken with a really badly scratched front element http://petapixel.com/2015/07/02/how-...ity-of-a-lens/ . I just take care of my lens and haven't got any scratches yet.
I think you better fix your pictures in post (taken in raw of course) than using cheap filters. Your overall result will probably be better.